All electrolytic capacitors are polarized, and carry markings to identify polarity of terminations.
Most small aluminium electrolytic capacitors carry a stripe on negative terminal side. In case of axial lead aluminium electrolytic capacitor, the stripe also carries arrow marks to point to negative terminal.
In addition, when lead wire are used as output terminals, negative terminal lead is shorter. So it çan be identified independent of other markings.
Large aluminium electrolytic capacitor with terminal disc has often red mark at base of + terminal.
In case of tantalum axial capacitor, often a + mark is placed to identify positive terminal.
What is polarization in a capacitor?
Not all capacitors are polarized, ones that are will be clearly marked with + and – where the leads go into the case.
Polarized capacitors are a type of capacitor called an electrolytic capacitor in which a chemical reaction on the surface of the capacitor’s anode forms an oxide layer that serves as the capacitor’s dielectric separator. Reversing the polarity would cause the oxide layer to dissolve causing the capacitor to short circuit, hence the need to be polarized.
Electrolytic capacitors are typically cylindrical with both leads coming out of one end of the can. They can be quite large. Failed electrolytic capacitors can split or even explode.
What does polarized capacitors mean?
A polarized capacitor has a dielectric material in it similar to the acid in a battery.
Capacitors consist of a sandwich of two conductors separated by an insulator. In a polarized capacitor the insulating material is a dielectric, meaning it becomes a dipole when the capacitor is charged.
Ordinary capacitors do not have a positive and negative side, but polarized capacitors do have a positive side and a negative side. When they are connected to a circuit you must take care to connect the positive side to positive and the negative side to negative. Failure to connect it properly could damage the capacitor. Under some circumstances it could overheat and be dangerous.
The large capacitance of electrolytic capacitors makes them particularly suitable for passing or bypassing low-frequency signals, and for storing large amounts of energy. They are widely used for decoupling or noise filtering in power supplies and DC link circuits for variable-frequency drives, for coupling signals between amplifier stages, and storing energy as in
